LOS ANGELES (AP) — Philip Seymour Hoffman suffered from a chronic medical condition that required ongoing treatment. An admitted drug addict who first sought professional help more than two decades ago, Hoffman apparently succumbed to his illness with an overdose despite a return to rehab last March.

A father of three with a thriving career, the Oscar winner died Sunday with a needle in his arm and baggies of what appeared to be heroin nearby. New York City medical examiners were conducting an autopsy on Hoffman’s body Monday as investigators scrutinize evidence found in his apartment, including at least four dozen plastic packets, some confirmed to have contained heroin.

His death, which came after a long period of sobriety that ended last year, “epitomizes the tragedy of drug addiction in our society,” said Dr. Nora Volkow, director of the National Institute on Drug Abuse.

“Here you have an extraordinarily talented actor who had the resources, who had been in treatment, who obviously realized the problem of drugs and had been able to stay clean,” she said, adding that Hoffman’s case shows how devastating addiction can be.

Success has no more bearing on drug addiction than it does on heart failure, doctors say: Both can be fatal without consistent care. And while rehab may be part of treatment, it’s no antidote. Amy Winehouse and Cory Monteith had both been to rehab before eventually dying from overdoses.

“Addiction is a chronic, progressive illness. No one can be cured,” said Dr. Akikur Reza Mohammad, a psychiatrist and addiction-medicine specialist who works as a professor at USC’s Keck School of Medicine and is founding chief of Inspire Malibu Treatment Center. “If someone is suffering from addiction, they cannot relax at any time. The brain neurochemistry changes… so these people are prone to relapse.”

The younger a person begins using drugs, the more likely he is to develop an addiction, Volkow said. Hoffman wasn’t specific about his poisons when he told CBS’ “60 Minutes” in 2006 that he used “anything I could get my hands on” before cleaning up with rehab at age 22.

He said in interviews last year that he sought treatment for heroin addiction after 23 years of sobriety.

Addiction causes chemical changes in the brain that remain long after a person stops using the substance, said Volkow, who described the condition as “a chronic disease with a very long duration.” Abstinence or substitute medication is often required to prevent the addict from losing control around his desired substance.

And just as someone who hasn’t ridden a bike for 20 years will still know what to do with a bicycle, an addicted brain exposed to its drug – even after a long break – will relapse to its old levels.

Studies have replicated this in animals, Volkow said: “Give them a tiny amount and they immediately escalate to same levels of drug taking as before” – which is why addiction is considered a chronic disease and overdose is common.

Hoffman’s “is a story that unfortunately is not infrequent – to have an individual who takes drugs in (his) 20s and stops for 20 years relapse in (his) 40s and overdose,” she said.

It’s not clear what motivated the actor’s return to drugs and what, if any, ongoing treatment he received after his rehab stint in 2013.

Director Anton Corbijn, who was with Hoffman at the Sundance Film Festival last month to promote the film “A Most Wanted Man,” said Hoffman’s death “came as much as a shock to me as to anyone else I’d imagine.” He said that when he spent time with the actor two weeks ago, he “seemed in a good place despite some issues he had to deal with,” but Corbijn did not elaborate.

Hoffman spoke to The Associated Press about the film at the festival, where he was dogged by paparazzi but otherwise calm. The actor, who could transform so convincingly into such varied characters on stage and screen, was generally a private person – something he said went with the job.

“If they start watching me (in roles) and thinking about the fact that I got a divorce or something in my real life, or these things, I don’t think I’m doing my job,” he said in the “60 Minutes” interview. “You don’t want people to know everything about your personal life, or they’re gonna project that also on the work you do.”

Because addiction has a genetic predisposition, celebrities are as likely as anyone else to suffer, though working in a field that may be more tolerant of drug use can increase a person’s chances.

“Addiction does not discriminate, the same way high blood pressure and diabetes do not discriminate,” Mohammad said, adding that 100 people die in the U.S. each day from drug overdoses. Those numbers are increasingly fueled by prescription painkillers, which tend to be opiates, like heroin.

Recovery from drug addiction is possible with treatment, lifestyle changes and awareness, doctors say. They may recommend inpatient rehabilitation for up to six months, followed by ongoing therapy and self-help meetings, such as those offered by 12-step programs. While intensity and type of treatment vary according to individual needs, Volkow said continuous treatment over five years has yielded the best results in studies so far.

“Continuity of care improves outcomes for individuals who are addicted to drugs,” she said, adding that it can be a “graded approach” that changes with time. “But you need continued awareness of the possibility of relapse. No matter how long you’ve been clean, if you take the drug, you’re at high, high risk of relapse.”